Methods and apparatus for logging underwater well bores



R.. Q. FIELDS 3,490,280 METHOD AND APPARATUS FOR LOGGING UNDERWATER WELL BORES Jan. 20,1970

Filed Jan. 22, 1968 wwfiawz h u N I K 1 Q G M a J 2 a 5 41 790 2 7 7 7 to 7 0O 2/ 5 l Bayer 62. F/e/dr INVENTOR.

United States Patent 0 3,490,280 METHODS AND APPARATUS FOR LOGGING UNDERWATER WELL BORES Roger Q. Fields, Houston, Tex., assignor to Schlumberger Technology Corporation, New York, N.Y., a corporation of Texas Original application Aug. 13, 1964, Ser. No. 389,389. Divided and this application Jan. 22, 1968, Ser. No. 699,703

Int. Cl. E21b 49/02 US. Cl. 73-152 19 Claims ABSTRACT OF THE DISCLOSURE The particular techniques and embodiments described herein as illustrated of the present invention relate to methods and exemplary apparatus for logging well bores that are completed and connected by a wellhead to flow lines leading to a remote location. More particularly, the invention disclosed herein is directed to methods and apparatus for performing various logging operations in underwater well bores having a submerged wellhead assembly and flow lines between such a wellhead and a central location at the surface of the water.

This application is a division of United States application Ser. No. 389,389, filed Aug. 13, 1964, now US. Patent 3,378,069.

It has become fairly common in recent years to drill for oil and gas in submerged locations such as the beds of swamps or lakes as well as the continental shelves that extend out into the ocean from the shores of various countries of the world. For purposes of safety as well as for obvious economic considerations, it is usually preferred to mount the wellhead assemblies for such underwater wells on the floor of the lake or ocean and, by means of devious conduits or flow lines leading therefrom, connect a number of such wellheads to a centrally located gathering system on a single platform above the surface of the water. Thus, as will be appreciated by those skilled in the art, subsequent completion and servicing operations to a given well are preferably performed by entering the well by way of its extended flow line and carrying out the desired operation from the surface platform. This technique is obviously less expensive than positioning a vessel over the well bore and temporarily disconnecting the flow lines from the Wellhead each time a completion or servicing operation is conducted.

To facilitate the performance of various completion and servicing operations from the surface platforms, the devious flow lines leading to each wellhead are typically arranged to descend in a gradual curve from the platform to the floor of the ocean or lake. Once the flow line reaches the bottom, it is extended therealong to its associated wellhead and then looped to form a largediameter reverse bend which brings the flow line into the wellhead in a generally vertical direction. In this manner, the flow lines will provide a relatively unobstructed passage through which various flexible or articulated tools having sealing members thereon can be readily introduced into a selected tubing string in any of the various well bores by applying a positive pumping pressure to the surface end of the particular flow line. To halt such tools in a known position, a so-called landing nipple or some similar abutment is permanently coupled to the lower end of each tubing string. Thus, when one of these so-called TFL or through the flow line tools is pumped into a particular flow line, once the tool reaches the landing nipple in the tubing string connected thereto, it will be halted. To retrieve such tools, it is generally preferred to apply pumping pressure in the reverse direction by way of either the annulus around the tubing string or a separate bypass conduit that enters the tubing string just above the landing nipple and below the sealing member on the tool. Such reverse pumping will, of course, unseat the tool from the landing nipple and return it back through the flow line to the surface platform. Heretofore, it has not been considered too practical, however, for one reason or another to conduct logging operations by way of the devious flow lines connected to a typical underwater wellhead assembly.

Accordingly, it is an object of the present invention to provide new and improved methods and apparatus for reliably conducting typical logging operations in submerged well bores located at a distance from a surface location and connected thereto by a devious flow line. This .and other objects of the present invention are attained by dispatching a logging tool through a tubular flow'line connected at its remote end to a tubing string that descends into an underwater well bore. Once the logging tool has reached a predetermined location in the well bore, fluid pressure is applied below the tool to raise the tool at a constant speed as it is performing one or more desired logging operations so as to obtain a record from which correlative depth measurements can be determined.

. The novel features of the present invention are set forth with particularity in the appended claims. The op- .eration, together with further objects and advantages thereof, may best be understood by way of illustration and example of certain embodiments when taken in conjunction with the accompanying drawings, in which: FIGURE 1 shows a typical subaqueous well bore;

FIGURE 2 depicts a typical logging tool as it might appear before beginning to conduct a logging operation in accordance with the present invention;

FIGURE 3 is similar to FIGURE 2 but Shows the logging tool as it completes a typical logging operation; and

FIGURE 4 is a cross-sectional view of a portion of an exemplary logging tool incorporating the principles of the present invention as it will appear while moving into position to begin a typical logging operation.

Turning now to FIGURE 1, a typical subaqueous well bore' 10 is shown and includes a string of casing 11 that is supported in a borehole 12 by the usual sheath of cement 13. To provide communication with an earth formation 14 containing oil and/ or gas, a tubing string 15 is dependently suspended in the casing 11 from a typical underwater wellhead 16 mounted on the floor of the body of water 17 above the wellhead. As is customary, the lower end of the tubing string is positioned a short distance above the producing formation 14 and a suitable packer 18 is set to isolate that portion of the cased well bore 10 below the packer from the remainder of the well bore thereabove. A tubular flow line 19 is extended from a platform (not shown) at the surface of the water 17 and, after being looped in a large-diameter reverse bend 20, connected to the wellhead 16 in communication with the tubing string 15. As is customary, a landing nipple 21 is secured to the lower end of the tubing string 15 and connected to aconduit 22 that provides a return passage to the surface platform. In this manner, when a TFL tool is dispatched through the flow line 19, the tool will be halted at the landing nipple 21. Then, when the tool is to be recovered, fluid pressure is applied to the conduit 22 that is extended from the surface platform.

Typical logging operations are, of course, customarily carried out during the drilling and completion of the well bore 10 before the drilling platform is moved to determine the relative depths and character of the various formations traversed by the borehole 12. Then by using the information obtained from such logs, the tubing string 15 is made up of a selected number of joints of a known length so that the packer 18 and landing nipple 21 will presumably be positioned at a known depth in relation to the formation 14. It is recognized, however, that since small-diameter tubing strings, as at 15, are frequently corkscrewed or otherwise deviated, the landing nipple 21 is often mislocated a significant amount. Thus, if this happens, future completion and workover operations relying upon the landing nipple 21 as a depth-correlation bench mark will be correspondingly inaccurate.

Heretofore, it has been necessary to carry out whatever post-completion logging operations are necessary from a platform directly over the subaqueous well bores, as at 10, so that the depth of the logging tool can be established by measuring the length of its suspension cable as it is payed out. Although this usual technique presents no problem where a permanent platform is erected over the subaqueous well bore, it is quite costly to carry out postcompletion logging operations in well bores such as at in view of the significant expenses of providing a temporary platform over the borehole 12 whether the drilling platform is left in position for the extra length of time required or a special platform is moved into position for the logging operation. In either event, the costs for providing a temporary platform over a subaqueous well bore, as at 10, to conduct logging operations in the usual manner are quite considerable.

The present invention will, however, now permit various logging operations to be conducted through the flow lines, as at 19, connecting the tubing string 15 to a remotely-located surface platform. Accordingly, as seen in FIGURE 2, a logging tool 23 is assembled on the surface platform (not shown) and introduced into the surface end of the flow line 19. As is typical with TFL tools, the logging tool 23 includes a housing or body 24 around which is mounted one or more swab cups or sealing members, as at 25, that are suitably sized and adapted to provide a sealing, but slidable, fit with the internal bores of the flow line 19 and tubing string 15. A second housing 26 is arranged to proceed the body 24 in the flow line 19 and tubing string 15 and is connected to the body by a predetermined length of a fairly stilf, but articulated or flexible, member 27. Although the choice of logging equipment that is enclosed in the housing- 26 will, of course, depend upon the number and desired types of logs to be obtained, the housing will typically include the power sources and appropriate circuitry necessary for obtaining one or more logs such as the various radioactivity logs.

Suitable recording means are also included in the tool 23 to record the desired logging measurements. Thus, it will be appreciated that the complete logging tool 23 will include all necessary logging circuitry and power sources. Although these various devices may all be enclosed in the housing 26, it may be desirable, for example, to enclose the power source and/ or the recorder in another housing, as at 28, above the body 24 and include one or more electrical conductors in the interconnecting member 27. Similarly, the housing 26 can also be comprised of two or more shorter rigid sections coupled together, as at 29 (FIGURE 3), by an articulated connection. Separation of the various devices in this manner will, of course, reduce the overall length of the housing 26 and facilitate the passage of the tool 23 through the flow line loops as at 20. Where necessary, one or more centralizers, as at 30 and 31 (FIGURES 2 and 3), may also be used to center the logging tool 23 and facilitate its passage through the flow line 19 and tubing string 15.

Irrespective of the many variations of circuitry and the like that can be used in assembling the logging tool 23 to obtain a desired log or logs, the tool is adapted to be dispatched through the flow line 19 and its associated tubing string 15 until the tool is finally arrested by the landing nipple 21. Once it is established that the logging tool 23 is in the position illustrated in FIGURE 2, it will,

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of course, be known that the depending housing 26 is suspended a known distance below the landing nipple 21. Thereafter, by circulating or pumping fluids from the surface through the bypass conduit 22, the logging tool 23 is moved upwardly in relation to the landing nipple 21 to allow the measuringdevices in the lower housing 26 to traverse the interval of earth formations, such as at 14, between the initial position of the lower housing shown in FIGURE 2 and the subsequent position thereof as seen in FIGURE 3. This will, of course, provide a logging record for the traversed interval of earth formations.

Accordingly, it will be appreciated that by moving the logging tool 23 upwardly from its position depicted in FIGURE 2 to that shown in FIGURE 3, a log will be obtained of one or more characteristics of the traversed interval of the earth formation 14. Thus, once the logging tool 23 is returned to the surface, the resulting log records can be readily compared with those log records obtained previously to determine just which formation interval has been logged.

Those skilled in the art will, of course, recognize that merely obtaining a record of the variations of the formation characteristic or characteristics being measured will be insufficient in many, if not most situations, to accurately determine just which formation interval has been logged. Stated another way, unless the logging record obtained can be in some manner be related to either depth or some dimensional relation or length of the interval logged, the logging record will be in most instances be inadequate.

Accordingly, in addition to providing a record of the variations in one or more measurable formation parameters, in the present invention a record is also obtained from which these measured parameters can be accurately related to at least the true length of the logged formation interval, if not its true depth as well. In general, this dimensional relation is obtained in the practice of the present invention by also obtaining a record of the passage of the logging tool 23 past either the landing nipple 21 or one or more other fixed detectable markers previously situated in the well bore 10. Then, once any of these relationships are obtained, the logging record or records obtained can be accurately correlated with previous logging records to determine its location in relation to the logged formation interval as well as the depth of the landing nipple 21.

It will be appreciated that if the logging tool 23 is positioned at the lower limit of the formation 14 (as will be governed by the length of the interconnecting member 27) and then moved upwardly at a constant speed into the landing nipple 21, the several measurements of formation parameters comprising the resulting log or logs will be uniformly distributed along a formation interval of a length equal to the initial spacing of the formation-measuring device in the housing 26 below the lower end of the landing nipple. Thus, if the interconnecting member 27 is of sufficient length to obtain representative fonmation measurements, the resulting log or logs can be readily compared with previous logs to ascertain with reasonable accuracy just which formation interval has been logged as well as its depth. The depth of this logged formation interval will, of course, have been determined on the previous logs from the cable measurements obtained while making these previous logs. Moreover, since passage of the formation-measuring device carried in the housing 26 into the landing nipple 21 will at least attenuate the formation measurements, the log or logs obtained with the logging tool 23 will also indicate the entrance of the lower housing into the landing nipple. This will, therefore, enable the depth as well as the position of the landing nipple 21 in relation to the formation 14 to be determined. It will be realized, of course, that the logging tool 23 can be moved at a constant rate as a logging record is being obtained by pumping fluids into the bypass line 22 at a constant flow rate.

Although a typical radioactivity log will show some indication of the passage of the lower housing 26 into the landing nipple 21, it would, ofcourse, be better to have previously mounted a bench mark such as a radioactive marker of some sort on the landing nipple before the well bore was completed. Similarly, the prior placement of one or more radioactive markers either on the casing 11 or in the formation 14 would also serve to provide distinctive indications of the passage of the tool 23 thereby.

It will be realized, however, that prior placement or radioactive markers may not necessarily have been done in every instance. Accordingly, in such instances, it is preferable that the logging tool 23 used in practicing the methods of the present invention include one or more anomaly detectors such as that shown in Patent No. 3,144,876 to Nick A. Schuster or some other sensing means adapted for detecting the presence of detectable anomalies in either the casing 11 and/or the tubing string 15. By mounting a collar locator, such as shown in the Schuster patent, at 32 in the upper housing 28, it will be appreciated that a detectable indication will be provided each time a coupling, as at 33, in the tubing string 15 is passed. Similarly, by mounting such a collar locator at 34 in the lower housing 26, a detectable indication will be obtained each time the tool 23 passes one of the casing collars, as at 35, -as well as when the lower housing enters the landing nipple 21. Thus, since the spacings of the couplings 33 relative to one another as well as to the landing nipple 21 and the relative spacing of the casing collars 35 are respectively known for any given well, a record of the passage of the tool 23 past these anomalies will provide a correlation from which the relative position of the landing nipple 21 to the formation 14 can be determined.

Stated another Way, the logging record obtained by the present invention can be readily compared with previous logs to identify the sought after producible formation 14. At the same time, the anomaly record or records obtained by the present invention will also provide a correlative depth measurement which will enable the upper and lower limits of the formation 14 to be accurately related to the landing nipple 21. Therefore, a servicing or completion tool such as any of those shown in the aforementioned parent application can subsequently be arranged to be at a predetermined location with respect to the formation 14 once the tool comes to rest on the landing nipple 21.

Accordingly, to practice the methods of the present invention, a logging tool, such as at 23, is dispatched through the flow line 19 and tubing string 15 until it reaches the landing nipple 21 as shown in FIGURE 2. Thereafter, by pumping fluids at a steady rate downwardly through the bypass conduit 22 as shown by the arrow 36, the logging tool 23 is moved upwardly to the position illustrated in FIGURE 3 to obtain a record of a series of measurements along the formation 14 as well as one or more indications of an anomaly such as provided by the collars 35 and/or couplings 33 as well as the landing nipple 21. Once the logging tool 23 is returned to the surface, by comparing the records obtained with previous logging records, the logged formation interval 14 can be identified and its relative location with respect to the landing nipple 21 accurately determined. This correlation will, therefore, enable any subsequent completion or servicing tool to be accurately arranged to be in a predetermined position in relation to the formation 14 when the tool is seated on the landing nipple 21.

It will be appreciated, of course, that more reliable logging and depth-correlation records can be obtained by arranging the logging tools of the present invention to provide an indication at the surface when it comes to rest on the landing nipple 21. Accordingly, a partial view is shown in FIGURE 4 of a logging tool 50 incorporating the principles of the present invention. As seen there, the

logging tool includes an intermediate body 51 that is tandemly connected by a fairly stiff but flexible cable 52 to a housing (not shown) therebelow in which suitable logging devices are enclosed. If desired, a second housing 53 can also be connected by the cable 52 above the body 51 and adapted to enclose such things as the recording devices and/or power sources for the logging devices in the lower housing. In such instances, the cable would, of course, have one or more conductors, as at 54, to electrically interconnect the various electrical devices in the upper housing 53 and lower housing. A centralizer 55 is preferably arranged on the cable 52 to keep it centered as the tool 50 is moving.

The body 51 is appropriately sized to pass through a flow line and the tubing string 15 and includes at least one sealing member 56 mounted thereon and arranged to slidably engage the inner wall of the flow line and tubing string. The lower end of the body 51 is appropriately formed to provide a seat 57 for engagement with an abutment 58 in the landing nipple 21. A central passage 59 is formed through the body 51 to snugly receive the cable 52 and a set screw 60 is provided so that the length of cable hanging below the body can be adjusted as required.

To provide a positive indication at the surface of the arrival of the logging tool 50 on the landing nipple 21, normally-closed valve means 61 are provided on the body 51 and releasably held in the closed position by position-responsive means 62 that are adapted for opening the valve means to bypass fluids around the sealing member 56 through a passage 63 in the body only when the body is seated on the landing nipple abutment 58. As shown in FIGURE 4, the valve means 61 are comprised of a flat annular plate 64 fitted on top of the body 51 and having a seal 65 on its underside adapted to seat around the upper end of the passage 63 so long as the late is in the illustrated position. Thus, so long as the plate 64 is seated on top of the body 51 and covers the passage 63, application of pressure to the tubing string 15 and flow line 19 will carry the logging tool 50 through these conduits toward the landing nipple 21.

To hold the plate 64 in its closed position as the logging tool 50 is moving toward the landing nipple 21, a rod 66 is dependently secured to the plate and extended through the body 51 into a recess 67 formed therein. A pivoted latch member 68 is mounted in the body recess 67 and provided with a hook 69 on its upper end that is releasably engaged on top of an enlarged shoulder 70 on the lower end of the rod 66 and normally maintained in this position by biasing means such as a spring 71. The opposite end of the latch 68 is arranged to project outwardly from the underside of the body 51 and is curved as at 72 so as to normally engage the inner wall of the flow line 22 and tubing string 15. Thus, so long as the body 51 is moving along the flow line 22 and tubing string 15, the spring 71 will retain the hook 69 on top of the enlarged shoulder 70 and the plate 64 will close the passage 63.

Once, however, the body 51 approaches the landing nipple 21, the wall-engaging end 72 on the latch is suitably proportioned to be cammed inwardly by the abutment 58 a suflicient distance to disengage the hook 69 from the shoulder 70. It will be appreciated, therefore, that once the hook 69 is disengaged from the rod shoulder 70, one or more springs, as at 73, normally compressed between the body 51 and plate 64 would function to open the passage 63 were it not for a second pivoted latch member 74. As seen in FIGURE 4, this second latch member 74 is arranged similarly to the first latch member 68 except that the hook 75 on this latch member 74 is disengaged from the shoulder 70 so long as the logging tool 50 has not yet reached the landing nipple 21. By arranging the latch member 74 so that its lower curved end 76 is spaced below the curved end 72 of the member 68 at least a distance equal to the height of the abutment 58, the latch members 68 and 74 cooperate to 7 keep the plate 64 seated until the body 51 is firmly seated on the abutment 58.

Thus, as illustrated in FIGURE 4, as the body 51 nears the abutment 58, the latch member 74 is moved by the abutment to engage its hook 75 with the shoulder 70 before the other hook 69 is disengaged. Then, as the body 51 moves into seating engagement with the abutment 58, the latch member 68 will be urged inwardly to release the hook 69 so that once the curved portion 76 of the latch 74 passes below the abutment, the hook 75 will be disengaged from the rod shoulder 70. Thus, once both of the hooks 69 and 75 are disengaged from the rod shoulder 70, the springs 73 will shift the plate 64 upwardly and open the upper end of the passage 63. To assure that an undetected inward protrusion in the flow line 19 or tubing string 15 does not prematurely operate both the latch members 68 and 74, the curved end 76 of the latch member 74 is sized to release the rod 66 only when the latch end moves outwardly below the landing nipple 21 a distance greater than that permitted by the inside diameters of the flow line and tubing string.

Once the valve means 61 are open, it will be appreciated that fluids can now be circulated from the surface through the tubing string 15 and through the passage 63 into the bypass conduit 22 for return to the surface. Opening of this fluid communication will, of course, result in a marked decrease of the indicated discharge pres sure of the fluid pumps at the surface and accordingly provides a positive indication that the logging tool 50 is in fact seated on the landing nipple 21. It will be realized, therefore, that by cooperatively arranging the latch members 68 and 74 in relation to the configuration of the abutment 58, the second latch will retain the plate 64 until the first latch is released by its movement into the narrower portion of the abutment. Then, once the latch member 68 is released, movement of the curved end 76 of the latch 74 below the abutment 58 will ultimately release the second latch member to open the passage 63.

Once the decreased pumping pressure at the surface indicates that the logging tool 50 is in fact seated in the landing nipple 21, the pump circulation is reversed to now pump fluids downwardly through the bypass conduit 22 so that the logging tool will begin its upward movement through the tubing string 15. It will be appreciated, of course, that with the bypass passage 63 now open, at least some of the circulated fluids would be needlessly bypassed. To avoid this, valve means are provided in the body 51 by enlarging the passage 63, as at 77, and forming a seat 78 therein to receive a ball check 79 loosely disposed in the enlarged bore 77. The lower end 80 of the enlarged bore 77 is arranged, such as by cutting grooves therein, so that the ball 79 will not be tightly seated on the lower end of the enlarged bore. Thus, once reverse circulation is started through the bypass conduit 22, the ball 79 will close the passage 63 to allow this fluid circulation to be fully effective to carry the logging tool 50 upwardly.

It will be realized, of course, that operation of the logging tool 50 can be accomplished in several manners. For example, the logging tool 50 can be equipped with a self-contained power source that is merely turned on just before the tool is introduced into the flow line 19 at the surface. This will, of course, cause the recorders in the tool 50 to operate the full time that the logging tool is in the flow line 19 and tubing string 15. On the other hand, various timed control arrangements can be used to initiate operation of the logging tool 50. Similarly, a messenger such as shown at 37 in FIGURE 2 of the aforementioned parent application can be arranged to initiate operation of the logging tool 50'. Various switching arrangements, such as shown in FIGURE 14 in the parent application, can also be adapted for actuation by movement of the latch members 68 and/or 72. For example, a switch, as at 81, could be provided to respond to inward movement of the latch member 68 to initiate operation of the logging tool 50. In any event, it will be appreciated that the present invention contemplates the inclusion of any one of a number of arrangements for selectively controlling the operation of the logging tool 50.

Accordingly, to use the logging tool 50 in the practice of the methods of the present invention, the cable 52 is secured in an appropriate position to insure that the formation-measuring devices in the lower housing will be a suflicient distance below the landing nipple 21 to obtain a representative log of the formation 14. Then, once the valve means 61 are in the closed position, the logging tool 50 is introduced into the flow line 22 and fluid circulation begun to carry the tool downwardly into the tubing string 15. Once the body 51 reaches the landing nipple 21, the cooperative action of the latch members 68 and 72 will release the plate 64 and open fluid communication through the bypass passage 63. As previously described, this selective opening of the bypass passage 63 upon the arrival of the tool 50 at the landing nipple 21 will cause an unmistakable reduction in the fluid pressure at the surface previously required to move the tool. Thus, once this indication is noted at the surface, reversal of the fluid circulation to begin pumping downwardly through the bypass conduit 22 will lift the logging tool 50 off of the landing nipple 21. It will be appreciated, of course, that where switches, such as at 81, are provided, typical holding circuits in the logging tool 50 will keep the logging circuitry operating even though the switch or switches reopen. Thus, by maintaining the reversed circulation at a preferably constant rate, the logging tool 50 will be moved upwardly in the manner shown in FIGURES 2 and 3 to obtain a log of the formation interval 14. It will, of course, be appreciated that once the plate 64 is released, it will remain above the body 51.

Once the logging tool 50 is returned to the surface and its logging record or records are compared with the previous logs, an accurate correlation will be obtained of the relation of the landing nipple 21 to the formation 14. Thus, by arranging a perforator, for example, such as shown in FIGURES 2 and 3 of the parent application, the perforating devices thereon can be accurately positioned to place perforations (not shown) at the desired depth to gain access to the formation 14.

Accordingly, it will be appreciated that the methods and apparatus of the present invention now permit the relative positions of a landing nipple and a selected formation to be accurately determined in subaqueous well bores that are served by devious flow lines leading to the surface. By obtaining representative logs and depth-correlation measurements with the present invention for comparison with previous logs and the like, the precise location of landing nipples in relation to earth formations therebelow can be determined so that completion and servicing tools subsequently introduced in the well can be accurately arranged to perform their intended operation with assurance that these tools are correctly positioned.

While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects; and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. An apparatus for logging a well which apparatus is arranged to be pumped through a flow line and comprises: a free housing sized for movement through the flow line of a well, means on said housing for providing a seal between said housing and flow line to sustain pumping pressure so that said housing may be pumped through the flow line, an electrical conduit means within said housing,

electrical switch means in said circuit, said electrical switch means being responsive to the location of said housing at a prescribed position in said flow line for closing said electrical cricuit means, and logging and log recording means connected to said housing and'said circuit means.

2. A method of establishing the relative location of a formation with respect to a selected position in the flow line of a well, which method comprises the steps of: connecting a positioning tool and well logging device in spaced relation to form a tool assembly with the connection providing sufficient flexibility to permit the tool string to be pumped through a flow line into a well, placing the tool string into a flow line, applying pressure to the flow line in one direction to move the tool string through the flow line into the well to place the positioning tool at a selected position, establishing an indication on a log in the logging device of the time at which the tool is placed at such selected position, applying pressure to the flow line in an opposite direction to move the tool string out of the well through the flow line, and logging the well while the tool string is moving out of the well to gather data on the well.

3. A method for determining the position of an earth formation traversed by a well bore in relation to a landing nipple located thereabove on the lower end of a pipe string with a logging tool having formation-logging means sized to pass through said landing nipple and sealing means connected thereto at a predetermined distance thereabove and sized to pass through said pipe string and be halted upon reaching said landing nipple, said method comprising the steps of: positioning said logging tool in the upper end of said pipe string and applying fluid pressure thereto suflicient to dispatch said logging tool to a first position on said landing nipple where said logging means are dependently suspended in said well bore therebelow at a depth believed to be below said earth formation; applying fluid pressure to said lower end of said pipe string sufficient to return said logging tool at a uniform speed to a second higher position and obtain a logging record of the well bore interval between said first and second tool positions; and after said logging tool is retrieved from said pipe string, correlating said logging record with a previous logging record of said well bore to determine whether said earth formation is located within said logged well bore interval.

4. The method of claim 3 wherein said formationlogging means provide an indication on said logging record of the passage of said logging means through said landing nipple and said second tool position is above said landing nipple whereby the' relative distance between said landing nipple and said earth formation can be determined by said correlating step.

5. The method of claim 3 wherein said logging tool further includes magnetic-anomaly detection means thereon for providing an indication on said logging record of the passage of said logging means through said landing nipple and said second tool position is above said landing nipple whereby the relative distance between said landing nipple and said earth formation can be determined by said correlating step.

6. The method of claim 3 wherein said formation-logging means include radioactivity-detecting means and said second tool position is above said landing nipple whereby passage of said formation-logging means through said landing nipple will provide a distinct indication on said logging record from which the relative distance between said landing nipple and said earth formation can be determined by said correlating step.

7. A logging tool adapted for obtaining a logging record in a well bore having a tubular landing nipple dependently suspended therein from the lower end of a pipe string extending out of the well bore to a distant location and comprising: a first body adapted for passage through such a pipe string and landing nipple; a second body adapted for passage through such a pipe string and having means thereon adapted for engagement with such a landing nipple to prevent said second body from passing therethrough; means flexibly interconnecting said first and second bodies and adapted to dependently support said first body whenever said second body has engaged a landing nipple; formation-logging means on said first body; and sealing means coupled to said second body and adapted for sliding engagement along the internal bore of such a pipe string.

8. The logging tool of claim 7 wherein said intercoglnecting means include a stiff but relatively flexible ca e.

9. The logging tool of claim 8 further including means adapted for adjusting the position of one of said tool bodies on said cable to vary the relative spacing between said tool bodies.

10. The logging tool of claim 7 wherein said formationlogging means include radioactivity-detecting means.

11. The logging tool of claim 7 further including magnetic-anomaly detecting means on at least one of said tool bodies.

12. The logging tool of claim 11 wherein said magneticanomaly detecting means are on said first tool body.

13. The logging tool of claim 11 wherein said magneticanomaly detecting means are on said second tool body.

14. The logging tool of claim 13 further including magnetic-anomaly detecting means on said first tool body.

15. The logging tool of claim 7 further including: bypass meansfon said second body and adapted, when open, for providing fluid communication across said sealing means; first means on said second body coupled to said bypass means and adapted to open said bypass means in response to arrival of said second body at such a landing nipple; and second means on said second body coupled to said first means and adapted to deactivate said first means so long as said second body is in such a pipe string and has not reached such a landing nipple.

16. The logging tool of claim 7 further including: bypass means on said second body and including a passage in said second body providing fluid communication between the upper and lower faces of said sealing means, and valve means on said second body for selectively opening and closing such fluid communication; and valveactuating means including an extendible member on said second body operatively arranged with said valve means and adapted for movement between an extended position and a retracted position to control said valve means in response to variations in internal diameter of such a pipe string and landing nipple, and means normally urging said extendible member toward its said extended position and adapted to maintain said extendible member in sliding contact with the inner wall of a pipe string containing said logging tool.

17. The logging tool of claim 16 wherein said extendible member is adapted to maintain said valve means closed so long as said extendible member is in its said extended position and to open said valve means whenever said extendible member is in its said retracted position so that movement of said second body into such a landing nipple will retract said extendible member and open fluid communication through said passage.

18. The logging tool of claim 16 wherein said extendible member is adapted to maintain said valve means closed so long as said extendible member is in its said retracted position and to open said valve means whenever said extendible member is in its said extended position so that movement of said second body into such a landing nipple will bring said extendible member below that landing nipple and out of contact therewith to open fluid communication through said passage.

19. The logging tool of claim 18 further including a second extendible member on said second body operatively arranged with said valve means and adapted for movement between an extended position holding said valve means closed and a retracted position to open said valve means, and means normally urging said second extendible member toward its said extended position and adapted to maintain said second extendible member in contact with the inner Wall of a pipe string containing said logging tool so that movement of said second body into such a landing nipple will bring said first-mentioned extendible member below that landing nipple and out of contact therewith as Well as bring said second extendible member into contact with that landing nipple and open said valve means.

References Cited UNITED STATES PATENTS 12/1952 Sewell 73-152 X 4/1959 Dean et a1. 166-4 10/1963 Ehlert 1664 X 8/1968 Dean 166153 X JERRY W. MYRACLE, Primary Examiner US. Cl. X.R. 

